To date, many different types of small-sized, large-aperture, wide-angle zoom lenses that are used in video cameras and electronic still cameras, such as digital cameras, have been proposed. Among them, for instance, one described in Japanese Patent Publication No. 2556048 is known that has a relatively light-weight front lens element and yields a bright image. The FNO is in the range 1.0-1.7 and the zoom lens is formed of, in order from the object side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. This zoom lens has some problems, however, in that the FNO changes during zooming and the image angle at the wide-angle end is rather small.
The objects of the present invention are to provide a small-sized, large-aperture, wide-angle zoom lens in which the FNO remains constant during zooming, and which ensures a wider image angle at the wide-angle end. Further, it is desired that the zoom lens satisfactorily correct aberrations over the entire range of zoom so as to provide bright images of high quality throughout the range of zoom. More specifically, the present invention aims to provide a small-sized, large-aperture wide-angle zoom lens having an FNO of approximately 1.4 with the FNO remaining constant during zooming, an image angle that is approximately 110 degrees, and a zoom ratio of about 2.6.